Timing of adjuvant chemotherapy initiation after surgery for stage III colon cancer

BACKGROUND. An important advance in medical oncology has been the use of adjuvant chemotherapy for lymph node-positive colon cancer. However, to the authors' knowledge, the effect of the interval between surgery and the initiation of chemotherapy on survival has not been investigated. METHODS. The authors analyzed predictors and outcomes of time intervals to treatment after surgery among patients older than 65 years who were diagnosed with stage III colon cancer between 1992 and 1999 using Surveillance, Epidemiology, and End Results (SEER)-Medicare data. Linear and logistic regression analyses were used to model predictors of delay, and Cox proportional hazards models were used to analyze the impact of treatment timing on survival. RESULTS. Among 4382 patients with colon cancer, 1122 patients (26%) began adjuvant chemotherapy within I month, 2391 patients (55%) began adjuvant chemotherapy in I to 2 months, 454 patients (10%) began adjuvant chemotherapy in 2 to 3 months, and 415 patients (9%) began adjuvant chemotherapy >= 3 months after surgery. Intervals of >= 3 months (delay) were associated with older age, increased comorbid conditions, well/moderately differentiated grade, and being unmarried. Colon cancer-specific mortality was associated with a delay in the initiation of chemotherapy (hazards ratio [HR], 1.48; 95% confidence interval [95% CI], 1.15-1.92), advanced age, increased comorbidity, poorly differentiated tumor grade, the presence of >= 4 positive lymph nodes, and undergoing surgery in a nomeaching hospital. All-cause mortality was associated with intervals > 2 months between surgery and chemotherapy (2 to 3 months: HR, 1.41; 95% CI, 1.15-1.74; >= 3 months: HR, 1.62; 95% CI, 1.31-1.99) compared with < 1 month. CONCLUSIONS. In the older population that was studied, only 9% of patients initiated adjuvant chemotherapy >= 3 months after the date of curative surgery. However, delay in initiation was associated with both cancer-specific and all-cause mortality. Determining whether these results were because of chemotherapy timing or other associated factors will require further study.